In a known manner, a turbomachine fan comprises a rotor disk bearing a plurality of blades whose roots are engaged and retained in substantially axial slots formed at the periphery of the disk. These blades are combined at their radially internal ends with platforms which internally define the annular flow path for the air stream entering the turbomachine.
Each blade of the fan may be formed in one piece with a platform. The blade is relatively heavy in that case, a factor which is manifested during operation by considerable mechanical stresses at the blade root, possibly causing cracks or splits to occur in this root. Moreover, the loss of a fan blade of this type results in significant damage in the turbomachine, and considerably increases the unbalance of the fan.
The fan blades and platforms may also be independent of one another. The platforms, termed inter-blade platforms, are then each attached and fastened to the fan disk between two adjacent blades. Each platform comprises internal radial lugs fastened to corresponding lugs of the disk by means of a number of systems of the nut and bolt type or pins mounted in orifices in the lugs of the platforms and in corresponding orifices in the lugs of the disk. These blades are not coupled to the platforms, thus making it possible to considerably reduce the mechanical stresses to which the blade roots are subjected during operation. It is then possible to reduce the size of the blade roots so as to lighten the fan and thus increase the performance of the turbomachine. Furthermore, in the event of losing a fan blade, the two platforms situated one on either side of the blade remain in place on the disk and do not cause any additional damage in the turbomachine. These two platforms additionally make it possible to protect the surrounding fan blades by preventing the debris from the lost blade coming into contact with the radially internal ends of the blades.
However, although the use of inter-blade platforms is advantageous for the reasons specified above, fastening these platforms by means of systems of the nut and bolt type or pins proves to be difficult, or even impossible, to achieve in the case of small engines having a diameter of around 1 m. The reason for this is that the fastening systems of the nut and bolt type are very bulky and cannot be used in a small-diameter engine. Furthermore, the interval between two adjacent fan blades and the space situated radially inside the platform are not sufficient to be able to manipulate the tools required to tighten these fastening systems. Manufacturers are thus constrained to use blades having integrated platforms in small-diameter engines.